(My theory is that ZXpand, which loads the game, has a problem with the Lambda 8300 ULA. Memory from the ZXpand is read and written fine. I assume the ULA has problem reaching it, so it is a timing problem that only occurs with the Lambda ROM. The problem is rarely with ZXpand ROM on Lambda.)

Well actually Lambda related z88dk files were patched to match the "old" Lambda ROM. It will be quite hard to make one binary that runs with the old and new ROM (as well as others). Currently the patched z88dk tree is still in a testing phase and "+lambda" now only compiles for the old ROM...